1. Field of the Invention
The present invention relates to an airship which can be propelled in any desired direction including front-rear, upper-lower and left-right directions.
2. Description of the Prior Art
Airships in the prior art include a gas chamber filled with gas having a specific gravity less than that of air and horizontal propelling means. Although airships additionally provided with vertical propelling means have been proposed, they have no yet been put to practical use.
These airships in the prior art mainly perform forward flight, as it is very difficult for them to ascend, descend and retreat. Even airships provided with vertical propelling means encounter difficulties in changing direction, for instance, from forward to upward movement because one of the propelling means must be stopped while the other propelling means is started.
In order to resolve these problems of the airships in the prior art, the present inventor previously proposed airships provided with erecting/laying type of propelling means, which can propel the aircraft in various directions including front-rear and upper-lower directions, in Japanese Patent Application No. 62-156478 (1987), for example.
While the proposed airships have remarkable merit in that the propelling direction can be chosen over the entire range within a plane in which the front-rear and upper-lower directions lie as viewed in the direction of flight, there still remains room for improvement because movement in the left and right directions cannot be effected only by the erecting/laying type of propelling means.
Further, the above-described airships in the prior art are subject to the following problems.
That is, among the airships in the prior art, those having propelling means for separately propelling the airship in the horizontal and vertical directions, respectively, with respect to the axis of the airship, are subject to the problem in that it is necessary to stop or start the respective propelling means each time the propelling direction is to be changed and so landing the airship in a narrow place is extremely difficult.
While the airships provided with the erecting/laying type of propelling means, which can select the propelling direction over the entire range within a plane including the front-rear and upper-lower directions with respect to the axis of the airship, exhibit improved take-off and landing performances, the ability of the airship to make fine movements in the left and right directions needs to be improved.